Isolation of a further anonymous informative DNA sequence from chromosome seven closely linked to cystic fibrosis.

A library prepared from flow-sorted chromosomes was used to isolate single-copy sequences from chromosome seven. One such sequence 7C22 has been shown to be polymorphic for an EcoRI restriction site and to be informative for the study of CF in approximately 35% of matings. The segregation of the 7C22 alleles was followed through nineteen informative families with more than one child affected by cystic fibrosis. We report that the locus for 7C22 is linked to the locus for cystic fibrosis at a recombination fraction of 0.045. This marker will prove useful in improving the accuracy and informativeness of prenatal diagnosis and in constructing a fine genetic map around the cystic fibrosis gene.     

Nitrospira marina gen. nov. sp. nov.: a chemolithotrophic nitrite-oxidizing bacterium

A new chemolithotrophic nitrite-oxidizing bacterium, for which the name Nitrospira marina is proposed, was isolated from the Gulf of Maine. N. marina is a Gramnegative curved rod which may form spirals with 1 to 12 turns. Cells have a unique periplasmic space and lack intracytoplasmic membranes and carboxysomes. N. marina is an obligate chemolithotroph, but best growth is obtained in a mixotrophic medium. N. marina may be one of the most prevalent nitrite-oxidizing bacteria in some oceanic environments. Type strain is field with American Type Culture Collection (ATCC 43039).     

Peritonitis during continuous ambulatory peritoneal dialysis in children.

The use of continuous ambulatory peritoneal dialysis (CAPD) in children has proved beneficial. However, peritonitis remains the major complication. A review of the incidence of peritonitis in 55 children (mean age 9.6 years) who underwent CAPD between 1978 and 1984 showed that there were 67 episodes of peritonitis (1 per 9.4 patient-months) in 33 of the 55. Three patients accounted for 22 of the episodes. In all cases, treatment with antibiotics, given intraperitoneally, was successful. Cephalothin was routinely given for infections due to gram-positive organisms, tobramycin for infections due to gram-negative organisms. Peritonitis recurred in seven patients, of whom five had to have their catheters replaced because of associated chronic infections of the deep peritoneal cuff, the exit site or the catheter tunnel. Although peritonitis was a common complication of CAPD in this population, it did not affect the success of the technique.     

A Cytokinetic Study of Small-Intestinal and Colonic Mucosa After Resection of 70% of the Small Intestine

Abstract. Pulse-labelling with tritiated thymidine and a fraction of labelled mitoses experiments have been performed in order to investigate the proliferative changes induced at various sites in the hyperplastic small-intestinal mucosa of rats previously subjected to resection of 70% of the small intestine. Proliferative activity in the colon was also studied.
In the distal ileum there is a significant reduction in cell cycle time (T_c) of cells at all levels within the crypt and the growth fraction falls. In the jejunum and proximal ileum the crypts contain an increased number of proliferating cells, but as the size of the maturation zone is also increased, there is no significant alteration in the relative number of proliferating cells per crypt. Nor does the distribution of proliferating cells in these crypts seem to alter. There is no general reduction in T_c at these sites, but there does appear to be a significant reduction in T_c on the part of the cells in the stem-cell zone at the crypt base.
In neither proximal nor distal colon was there any significant proliferative change apparent after small-intestinal resection.     

Comparison of the Limulus amoebocyte lysate test with plate counts and chemical analyses for assessment of the quality of lean fish.

The quality of lean fish was assessed simply and rapidly with Limulus amoebocyte lysate. The endotoxin levels agreed with aerobic plate counts and chemical indices of spoilage. Correlation between level of endotoxin and level of total volatile bases was found to be highly significant (r = 0.8579; P less than 0.001).     

Purification of the receptor for nerve growth factor from A875 melanoma cells by affinity chromatography

The receptor for nerve growth factor (NGF) has been purified to near homogeneity from octylglucoside extracts of A875 melanoma cell membranes by the use of repetitive affinity chromatography on NGF-Sepharose. Elution of purified receptor (NGF receptor) was accomplished with 0.15 M NaCl, pH 11.0, containing phosphatidylcholine and octylglucoside. Chromatography on two columns of NGF-Sepharose yielded a 1500-fold purification of the receptor, as assessed by 125I-NGF binding, and permitted recovery of 9% of the total binding activity in the soluble extract. Scatchard analysis of equilibrium binding of 125I-NGF provided similar Kd values for NGF receptors in soluble extracts of A875 membranes (2.2 nM) and with purified NGF receptor (3.1 nM). Examination of NGF receptor after electrophoresis on sodium dodecyl sulfate-polyacrylamide gels revealed the presence of two major peptides, of Mr = 85,000 and Mr = 200,000. Affinity labeling experiments, done with 125I-NGF and A875 cells, soluble extracts of A875 cell membranes, and purified receptor, show that both of these components of the NGF receptor can be specifically cross-linked to 125I-NGF.     

Genetic and physical studies of restriction-deficient mutants of the Inc FIV plasmids R124 and R124/3

Summary R124 and R124/3 are R plasmids that carry the genes for two different restriction and modification systems. The phenotype of strains carrying either of these plasmids along with the F'lac ⁺ plasmid, is restriction-deficient (Res^-). The Res^- phenotype is not due to selection of preexisting mutants but rather to a complex mutational event caused by the F plasmid. Restriction-deficient mutants carry extensive deletions and other DNA rearrangements. Tn7 insertion is used to locate the restriction gene. Many of the Res^- mutants are genetically unstable and revert at exceptionally high frequencies. Reversion is accompanied by DNA rearrangements which result in a net gain of 9 kb of DNA. F derivates of F⁺ which do not cause restriction-deficiency but do cause deletion were used to distinguish between the DNA rearrangements associated with restriction-deficiency and those associated with deletion. From Res⁺ revertants of strains carrying F'lac ⁺ and R124 or R124/3 we have isolated F plasmids that now carry the genes for the R124 or R124/3 restriction and modification systems. It is suggested that interaction between part of the F plasmid and that segment of the R plasmid which controls the switch in Res-Mod specificity which has been observed (Glover et al. 1983) is responsible for the production of restriction-deficiency.     

Partial Purification and Characterization of a Glycoprotein Cell Fusion Hormone from Griffithsia pacifica, a Red Alga

In filaments of the red alga Griffithsia, dead intercalary cells are replaced by the process of cell repair by cell fusion. This process is coordinated by a morphogenetic cell fusion hormone, rhodomorphin, which accelerates cell division and induces the production of a specialized repair cell. We have isolated rhodomorphin from Griffithsia pacifica Kylin and have purified it by concanavalin A affinity chromatography, hydrophobic interaction chromatography, and gel filtration chromatography. This molecule binds specifically to concanavalin A, is proteinase sensitive, and is inactivated by short treatments at temperatures of 50°C or above. It therefore appears that rhodomorphin from G. pacifica is a glycoprotein; its molecular weight, as estimated by gel filtration, is approximately 14,000.     

Construction of recombination-deficient strains of Pseudomonas aeruginosa

Summary The rec-102 mutation had pleiotropic effects in Pseudomonas aeruginosa: low recombination proficiency in conjugation and transduction; high UV sensitivity; inability to induce pyocin R2 by mitomycin C; and increased susceptibility to mitomycin C and nalidixic acid. The rec-102 locus was mapped by R68.45-mediated conjugation in the 45 min region of the PAO chromosome, between argF and thr-9001. By selection for a marker in this region, rec-102 can be introduced into a P. aeruginosa strain of interest using an R68.45 rec-102 donor. The recombination-deficient strains constructed in this way were phenotypically similar to Escherichia coli recA mutants.